Processing system

ABSTRACT

In a first aspect, a first substrate processing system is provided that includes (1) a chamber having a plurality of openings through which a substrate may be transported; (2) a substrate carrier opener coupled to a first one of the plurality of openings; (3) a thermal processing chamber coupled to a second one of the plurality of openings; and (4) a wafer handler contained within the chamber, having a substrate clamping blade and a blade adapted to transport high temperature substrates. Numerous other aspects are provided, as are methods and computer program products in accordance with these and other aspects.

This application claims priority from U.S. Provisional PatentApplication Ser. No. 60/305,679, filed Jul. 15, 2001, titled “ProcessingSystem” (Attorney Docket No. 6022/L), which is hereby incorporated byreference herein in its entirety.

BACKGROUND

In the field of substrate processing, improvements in substrate handlingspeed and reliability can translate into significant cost savings, andimproved substrate quality. Likewise, a reduction in footprint (i.e.,the projected floor space occupied by a processing system), and/or areduction in equipment cost and complexity may result in reduced costper substrate processed. Accordingly, substrate processing systems thatimprove throughput speed, reduce equipment cost and complexity and/orreduce the potential for substrates to be exposed to particles aredesired.

SUMMARY

An inventive substrate processing system that transfers both hot andcold substrates is provided, as is an inventive method of transferringand processing substrates within the system. Also employed are inventiveapparatuses and methods for sensing substrates on a substrate handlerblade, for employing a ventilated valve assembly to deter toxicprocessing gases from entering an ambient environment, and/or forcooling substrates within a transfer chamber. Each such apparatus andmethod may be employed with the inventive system or with otherprocessing systems and methods, as will be apparent from the figures anddescription provided below.

More specifically, in a first aspect of the invention, a first substrateprocessing system is provided that includes (1) a chamber having aplurality of openings through which a substrate may be transported; (2)a substrate carrier opener coupled to a first one of the plurality ofopenings; (3) a thermal processing chamber coupled to a second one ofthe plurality of openings; and (4) a wafer handler contained within thechamber, having a substrate clamping blade and a blade adapted totransport high temperature substrates.

In a second aspect of the invention, a second substrate processingsystem is provided that includes (1) a chamber having a plurality ofopenings through which a substrate may be transported; and (2) a waferhandler contained within the chamber having a substrate clamping bladeand a blade adapted to transport high temperature substrates.

In a third aspect of the invention, a substrate handler is provided thatincludes (1) a substrate clamping blade; and (2) a blade adapted totransport high temperature substrates.

In a fourth aspect of the invention, a valve assembly is provided thatis adapted to seal an opening in a chamber. The valve assembly includesa housing having a first opening on a first side and a thresholdportion. The housing is adapted for coupling to a chamber surface havingan opening therein, such that a substrate may be transferred through thefirst opening and the chamber opening and such that the thresholdportion is positioned between the first opening and the chamber opening.The threshold portion has one or more inlets adapted to supply a curtainof gas across the chamber opening. The valve assembly further includes asealing surface positioned within the housing to selectively (1) sealthe chamber opening, and (2) retract from the chamber opening so as notto obstruct substrate passage therethrough. Numerous other aspects areprovided, as are methods and computer program products in accordancewith these and other aspects of the invention.

Other features and aspects of the present invention will become morefully apparent from the following detailed description, the appendedclaims and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of an exemplary aspect of the inventivesystem;

FIG. 2 is a schematic side elevational view of an exemplary aspect of aninventive substrate handler;

FIG. 3A is a top plan view of a clamping substrate handler blade havinga substrate sensor coupled thereto;

FIG. 3B is a top perspective view of hot substrate handler blade havinga substrate sensor coupled thereto;

FIG. 3C is a top plan view of the substrate handler of FIG. 2;

FIGS. 4A-E are views of a cooling platform that may be employed withinthe system of FIG. 1; and

FIG. 5 is an exploded side isometric view of a valve assembly that maybe employed within the system of FIG. 1.

DETAILED DESCRIPTION

FIG. 1 is a top plan view of an inventive processing system 11. Theprocessing system 11 comprises a chamber 13 having a plurality ofopenings 15 a-d through which a substrate may be transferred. Eachopening 15 a-d preferably is positioned at a similar elevation (referredto herein as the wafer exchange elevation). In the embodiment shown,openings 15 a-b are located on a first side of the chamber 13 andopenings 15 c-d are located on a second side of the chamber 13, oppositethe first side of the chamber 13. A station 17 a adapted to open asealed wafer carrier (i.e., a pod opening station 17 a) is coupled tothe opening 15 a and a pod opening station 17 b is coupled to theopening 15 b. Pod opening stations are well known in the art, and anexemplary pod opening station is described in detail in U.S. Pat. No.6,082,951 issued Jul. 4, 2000, the entire disclosure of which isincorporated herein by this reference.

Coupled to the openings 15 c-d are thermal processing chambers 19 a-bsuch as the commercially available RADIANCE™ Chamber manufactured byApplied Materials of Santa Clara Calif., or any other chamber thatelevates substrates to temperatures above 70° C. for example andpreferably to approximately 600° C.

A cooling station 21 may be contained within the chamber 13 (e.g.,coupled to the same datum plate as the substrate handler, and at ahigher elevation than the chamber openings) and may comprise one or moreplatforms designed to support and cool a substrate as is known in theart. An inventive cooling station is shown in FIGS. 4A-E and describedbelow with reference thereto.

Also contained within the chamber 13 may be a track 23 that extends asufficient distance so that a substrate handler coupled to traveltherealong may pick up or place substrates to or from any of the podopening stations 17 a-b, processing chambers 19 a-b, or cooling station21. Mounted so as to travel along the track 23 is a substrate handler 25(FIG. 2) having both a blade adapted to clamp a substrate in placethereon (i.e., a clamping blade 27), as shown in FIG. 3A, and a bladeadapted to transport a hot substrate, for example, a substrate having atemperature of above 70° C., and in one embodiment a temperature ofapproximately 600° C. or higher (i.e., a hot blade 29), as shown in FIG.3B. The substrate handler 25 may also comprise a pair of verticallystacked independently extendable arms 30 a-b each having one of theclamping blade 27 and the hot blade 29 coupled thereto, as shown in theside elevational view of FIG. 2.

Except for the inventive hot blade 29, the substrate handler 25 may be acommercially available robot manufactured by Yaskawa Japan. For example,the substrate handler 25 may employ a central canister 32 (FIG. 2) thatrotates at least 180 degrees, and has two independently extendable robotarms (e.g., arms 30 a-b in FIG. 3C) coupled thereto. Thus when thecanister 32 lifts, lowers or rotates, the two arms lift, lower androtate together therewith. The two arms are vertically offset (FIG. 2)such that the blade coupled to one arm (e.g., hot blade 29) is above(and in approximately the same footprint) as the blade coupled to theother arm (e.g., clamping blade 27). In order to insert and extract asubstrate from an opening, the central canister 32 elevates to positionthe correct blade in the plane of the opening. Other robotconfigurations having acceptable reach may be employed, without thetrack. Also two robots may be contained within the chamber 13 and thusthe track 23 may be omitted.

The two independently extendable and retractable arms 30 a-b, and theclamping blade 27 and hot blade 29 coupled thereto allow the processingsystem 11 to transfer substrates much more efficiently than is possiblewith conventional thermal processing systems. Because the clamping blade27 includes a mechanism for clamping substrates, the clamping blade 27may transport substrates more quickly than can a blade that does notinclude a clamping mechanism. Although other clamping mechanisms may beemployed, an exemplary clamping mechanism is shown in the top plan viewof FIG. 3A. The clamping mechanism comprises a plunger 31 and a pair ofedge stops 33 (e.g., formed from a high temperature material such asVESPEL or PEEK in at least one embodiment). In operation, after theclamping blade 27 has completed a programmed sequence of movements thatcauses the clamping blade 27 to lift a substrate (not shown) from a pod(e.g., positioned at one of the pod opening stations 17 a-b), theprocessing chambers 19 a-b, or the cooling station 21, a controller Ccauses the plunger 31 to gradually move forward to a position whereinthe substrate is firmly held between the edge stops 33 and the plunger31. The plunger 31 may be designed so as to interact with a lightdetector (described below) to thereby detect whether or not a substratehas been properly clamped.

In the example of FIG. 3A, the plunger 31 has an opening 35 located suchthat a light beam L1 emitted by an emitter 37 passes through the opening35 (and strikes a light sensor 39) only when the plunger 31 is in theposition where it contacts the edge of a properly positioned substrate.In all other positions solid portions of the plunger 31 block the lightbeam L1. In this manner no light beam is detected both when the plunger31 is in its retracted position (prior to substrate placement on theclamping blade 27) and when the plunger 31 has extended beyond theposition where it should contact the edge of a properly positionedsubstrate.

A controller (e.g., controller C in FIG. 3A) coupled to the light sensor39 may signal a miss-clamp and prevent the clamping blade 27 from movingwhen the plunger 31 extends beyond the proper substrate clampingposition. Thus the clamping blade 27 may allow both faster substratetransfer, and may allow the processing system 11 to be less expensive,as fewer sensors need to be stationarily mounted therein. The emitter 37and light sensor 39 may comprise any conventional light source anddetector.

The expense of the processing system 11 may be further reduced ascompared to conventional systems by coupling a sensor to the hot blade29, as shown in the top perspective view of FIG. 3B. The hot blade 29has a support bracket portion 29 a and a blade portion 29 b as shown.The hot blade 29 has a light emitter 41 and a light detector 43positioned (through use of high temperature fiber optic cables 44 a, 44b and fiber optic support brackets 44 c, 44 d) such that a properlypositioned substrate S blocks a light beam L2 from travelingtherebetween. In order to endure contact with hot substrates, the hotblade 29 may be comprised of quartz or a similar high temperaturematerial. In order to prevent light from the emitter 41 from coupling tothe quartz blade 29 and traveling though the quartz to the lightdetector 43 (as shown by arrow 45) the portion of the hot blade 29adjacent the emitter 41 and adjacent the detector 43 may be coated witha non-refractive coating such as silicon carbide. For example, theemitter and/or detector may be surrounded by metal to deter erroneousdetection of reflections, and the beam gain threshold may be adjusted tocompensate for reflection and refraction (e.g., via a suitableamplifier). Accordingly, when the detector 43 does not receive the lightbeam L2 emitted by the emitter 41, the hot blade 29 detects that asubstrate is properly positioned on the hot blade 29; when the lightsignal from light beam L2 is detected, a substrate is either absent oris improperly positioned. The controller C (FIG. 3A) may preventmovement of the hot blade 29 when a substrate is expected to be properlypositioned on the hot blade 29 and the light beam is not broken.

In at least one embodiment, the support bracket portion 29 a of the hotblade 29 may comprise a stainless steel quartz/metal support bracket,and the blade portion 29 b may comprise quartz (coupled via aquartz/metal plate 29 c). Other materials may be employed.

Because both the clamping blade 27 and the hot blade 29 have sensorsadapted to sense when a substrate is properly positioned on the clampingblade 27 or on the hot blade 29 (e.g., both blades employ integratedwafer on blade sensors), there is no need for stationary “substrate onblade” sensors. Because the substrate handler 25 comprises both aclamping blade and a hot blade, considerable throughput advantages canbe achieved as will be understood from the operational descriptionprovided below.

In operation a substrate carrying pod is placed on the pod openingstation 17 a and the pod door of the pod is opened. The substratehandler 25 travels along the track 23 to a position in front of theopening 15 a associated with the pod opening station 17 a. Assuming theclamping blade 27 is at the wafer exchange elevation, the substratehandler's extendable arm 30 b extends carrying the clamping blade 27through the opening 15 a into the pod opening station 17 a such that theclamping blade 27 is positioned below a first substrate. The substratehandler 25 then elevates slightly such that the clamping blade 27 liftsthe first substrate from the pod's internal supports. The controller Crecognizes that a substrate should be in position on the clamping blade27, and the plunger 31 (FIG. 3A) is actuated so as to slowly move towardthe edge stops 33, gently pushing the substrate forward such that thesubstrate is held in place between the plunger 31 and the edge stops 33.

As previously described, the clamping blade sensor (e.g., light emitter37 and light sensor 39) may sense that the substrate is properlyclamped. If the substrate is determined to be properly clamped, theextendable arm 30 b retracts, the substrate handler 25 rotates theclamping blade 27 to face the opening 15 c (FIG. 1) and travels alongthe track 23 to position the clamping blade 27 in front of the opening15 a (if necessary). The opening 15 c opens and the extendable arm 30 bextends carrying the first substrate into position above a wafer support(not shown) contained within the processing chamber 19 a. All of theabove described substrate transport steps may occur at higher speedsbecause the substrate is clamped on the clamping blade 27.

Once within the processing chamber 19 a, the plunger 31 (FIG. 3A)retracts and the first substrate is lifted from the clamping blade 27 bya lift mechanism (not shown) contained within the processing chamber 19a, and/or by lowering the clamping blade 27 so as to transfer the firstsubstrate onto a plurality of support pins or other supporting structure(not shown). Thereafter the above sequence repeats with the clampingblade 27 placing a second substrate within the processing chamber 19 b.As soon as thermal processing of the first substrate is complete, thehot blade 29 is positioned at the wafer exchange elevation, the opening15 c opens, the extendable arm 30 a extends and the hot blade 29retrieves the hot first substrate (e.g., lifts the hot first substratefrom the support pins). Thereafter, the hot blade 29 retracts, and thesubstrate handler 25 elevates to position the clamping blade 27 at thewafer exchange elevation. The clamping blade 27 then extends carrying athird substrate into the processing chamber 19 a. In this manner, notonly is a hot (processed)/cold (unprocessed) substrate exchange able tobe performed via a single substrate handler, the exchange is also ableto take place without intermission (i.e., without requiring thesubstrate handler 25 to travel to other locations for placement of theprocessed substrate and pickup of the unprocessed substrate).Thereafter, the hot first substrate may be carried to a support shelf(not shown) of the cooling station 21, and transferred to the supportshelf (e.g., via the support shelf's lifting mechanism and/or vialowering of the hot blade 29). Once placed on the support shelf, thefirst substrate cools (e.g., air cools or cools via a cooled plate suchas that of FIGS. 4A-E).

Thereafter the substrate handler 25 may employ the hot blade 29 toextract the processed hot second substrate from the processing chamber19 b, and transport the second substrate to the cooling station 21 forcooling. If the first substrate has been cooling for a sufficient time,the clamping blade 27 may extract the cooled first substrate from thecooling station 21 and quickly return the first substrate to the podopening station 17 a.

As is apparent from the above description, the inventive processingsystem 11 is able to increase throughput by using a clamping blade totransfer substrates whenever they are not hot. Also, because both theclamping blade 27 and the hot blade 29 may have substrate sensors thatverify proper substrate clamping or positioning, the processing system11 may avoid the additional expense of stationary substrate on bladesensors (e.g., sensors that are not located on a blade) that wouldotherwise be located at various positions within the processing system11 (e.g., in front of each location where substrate exchange occurs).

The inventive processing system 11 may also employ other features tofurther enhance operation. For example, the clamping blade 27 and/or thehot blade 29 may have one or more sensors mounted on the leading end ofeach blade and directed forward (toward the direction the bladetravels). The sensor(s) may detect that a substrate is present in agiven slot or location, before the blade travels into positiontherebelow. Such sensors are provided for example on substrate handler'ssuch as those manufactured by Yaskawa Japan.

FIG. 4A is a perspective view of a first exemplary embodiment of thecooling station 21 of FIG. 1. The cooling station 21 includes aplurality of cooling platforms 102 a-c each configured to cool asemiconductor wafer as described below. While three cooling platforms102 a-c are shown in FIG. 4A, it will be understood that the coolingstation 21 may comprise fewer or more cooling platforms. FIG. 4B is aperspective view of the cooling station 21 of FIG. 4A that shows aninternal cooling structure of the top cooling platform 102 a (describedbelow).

Each cooling platform 102 a-c is coupled to a manifold 104 (e.g., viabrazing, bolts, screws and/or some other fastening technique), which isin turn coupled to a support bracket 106 (e.g., aluminum or any othersuitable material). FIG. 4C is a perspective view of the cooling station21 of FIG. 4A that shows one method of coupling an internal coolingstructure of each cooling platform 102 a-c to the manifold 104 (e.g.,brazing). FIG. 4D is a perspective view of an internal cooling structureof each cooling platform 102 a-c.

With reference to FIGS. 4A and 4B, a plurality of lift mechanisms 108a-c are coupled to the support bracket 106 that allow semiconductorwafers (or other substrates) to be lowered onto or lifted from thecooling platforms 102 a-c (as described below). Each lift mechanism 108a-c includes a lift portion 110 a-c and a lift pin support arm 112 a-ccoupled to the lift portion 110 a-c. Each lift pin support arm 112 a-cincludes a plurality of lift pins 114 a-c that may lift and lowerthrough holes (described below) in a respective cooling platform 102 a-cas the lift support arm 112 a-c is lifted and lowered via the liftportion 110 a-c. Semiconductor wafers thereby may be raised from andlowered onto each cooling platform 102 a-c (e.g., for removal from andplacement onto each cooling platform 102 a-c). The lift mechanisms 108a-c may comprise, for example, 1.6 mm bore pneumatic cylinders, althoughany conventional lift mechanisms may be similarly employed. Oneexemplary lift mechanism is a Device Net EV pneumatic block. Each liftmechanism 108 a-c may include sensors for detecting lift cylinderposition (e.g., two or more conventional magnetic switches). The liftpins 114 a-c may comprise stainless steel lift pins having ceramic ballsor tips (not shown) disposed thereon which contact semiconductor wafersduring cooling. Other lift pin materials may be used.

In one embodiment of the invention, each cooling platform 102 a-ccomprises a top portion 116 a-c and a bottom portion 118 a-c that encasea cooling fluid line 120 a-c (FIGS. 4C and 4D). The top portions 116 a-cand bottoms portions 118 a-c may comprise, for example, nickel-platedaluminum or another suitable material, and may be coupled together(sandwiching the cooling fluid lines 120 a-c therebetween) via anysuitable coupling mechanisms (e.g., screws, bolts, adhesives, etc.).Thermal grease (e.g., MASTERBOND's SUPREME 10AOHT) may be employedbetween the top portions 116 a-c, the bottom portions 118 a-c and thecooling fluid lines 120 a-c to increase thermal transfer between thesecomponents. The cooling fluid lines 120 a-c may comprise copper,stainless steel or any other appropriate material. In one embodiment,the top portion 116 a-c of each cooling platform 102 a-c is blackanodized aluminum.

In an alternative embodiment for the cooling platforms 102 a-c, eachcooling fluid line 120 a-c is placed between the top portion 116 a-c andbottom portion 118 a-c during casting of the top portion 116 a-c andbottom portion 118 a-c (e.g., each cooling platform 102 a-c comprises anintegrally formed unit). In such an embodiment, the cooling platforms102 a-c require no assembly and no thermal grease as the top and/orbottom portions (e.g., aluminum) completely surround the cooling fluidlines (e.g., stainless steel or copper). Cooling fluid lines having ahigher melting temperature than the top/bottom portions are preferred sothat the cooling fluid lines do not deform during cooling platformformation.

Regardless of the exact construction of the cooling platforms 102 a-c,it may be desirable to have the top portion 116 a-c of each coolingplatform 102 a-c thicker than the bottom portion 118 a-c. That is, ifthe cooling fluid line of a cooling platform 102 a-c is too close to thetop surface of the cooling platform 102 a-c, more cooling may occur inregions of the top surface that reside directly above the cooling fluidline. A larger (e.g., thicker) top portion 116 a-c provides more thermalmass and may allow for more uniform cooling of each cooling platform 102a-c. In one embodiment of the invention, the total thickness of eachcooling platform 102 a-c is about 1.062 inches, although otherthicknesses may be employed.

In at least one embodiment of the invention (FIG. 4B), the top portion116 a-c of each cooling platform 102 a-c includes one or more of (1)insulating pads 122; (2) alignment pins 124; and (3) through holes 126that allow the lift pins 114 a-c to extend therethrough. The bottomportion 118 a-c of each cooling platform 102 a-c may be similarlyconfigured with lift pin through holes (not shown).

The insulating pads 122 may comprise, for example, insulating ballspartially embedded within the top portion 116 a-c, such as ¼″ siliconnitride, carbon or ceramic balls that extend about 0.040 inches abovethe top surface of each cooling platform 102 a-c. The insulating pads122 may be, for example, high temperature epoxy bonded to the topportion 116 a-c of each cooling platform 102 a-c. In one embodiment, asufficient number and appropriately spaced arrangement of insulatingpads 122 are employed on each cooling platform 102 a-c to ensure that asemiconductor wafer placed on the insulating pads 122 does not contactthe top surface of each cooling platform 102 a-c. Preventing directcontact between a semiconductor wafer and the top surface of the coolingplatforms 102 a-c may (1) reduce particle generation; and (2) reducenon-uniform cooling of the semiconductor wafer (as non-uniformly coolinga wafer may damage the non-uniformly cooled portion of the wafer orshatter the wafer).

In one embodiment, a 0.040 inch air gap may exist between asemiconductor wafer placed on the insulating pads 122 and the topsurface of the cooling platform 102 a-c employing the insulating pads122. Other air gap spacing may be used. When embedded balls are used asthe pads 122, the depth of the ball holes within the top portion 116 a-cof each cooling platform 102 a-c may affect the distance between the topof the cooling platform 102 a-c and the cooling fluid line 120 a-cdisposed therein, and/or the overall thickness of the cooling platform102 a-c.

The alignment pins 124 may comprise, for example, quartz or any othersuitable material. In one embodiment, the alignment pins 124 comprisepolished quartz (e.g., to minimize particle generation when a wafercontacts the pins 124) that is angled so as to allow a wafer to slidethereagainst without sticking. One exemplary angle is about 25 degreesfrom a center axis of each pin, although other angles may be employed.The alignment pins 124 allow accurate positioning of a semiconductorwafer on each cooling platform 102 a-c. The use of alignment pins duringwafer positioning is known in the art and is not described furtherherein.

With reference to FIGS. 4B and 4C, the cooling fluid line 120 a of thecooling platform 102 a (and the cooling fluid lines 120 b-c of thecooling platforms 102 b-c shown in FIG. 4D) comprises a hollow tubeconfigured to deliver cooling fluid (e.g., water and/or a refrigerant)to the cooling platform 102 a. In this manner, the top portion 116 a anda semiconductor wafer placed thereon may be cooled. With reference toFIG. 4B, in one embodiment of the invention, the cooling fluid line 120a is specifically configured to reside within a single plane (e.g., thex-y plane in FIG. 4B). In this manner, the thickness of the coolingplatform 102 a is reduced (when compared to a design wherein the coolingfluid line does not reside entirely within a single plane). Such a“multi-plane” design may be employed if desired, and is shown, forexample, in FIG. 4E.

The cooling fluid line 120 a of FIGS. 4B and 4C has an inlet 128 and anoutlet 130 both coupled to the manifold 104. In one embodiment, theinlet 128 is positioned close to the outer edge of the cooling platform102 a (as shown) and the outlet 128 is positioned close to the center ofthe cooling platform 102 a (as shown). The inlet 128 is positioned closeto the outer edge of the cooling platform 102 a because (1) the largestpercentage of the cooling platform's mass resides close to the outeredge of the cooling platform 102 a; and (2) cooling fluid travelingthrough the cooling fluid line 120 a is coolest at the inlet 128. Inthis manner, the “coolest” cooling fluid cools the largest portion ofthe cooling platform 102 a.

The remainder of the cooling fluid line 120 a winds from the inlet 128to the outlet 130 through the cooling platform 102 a in a non-spiralingmanner (unlike spiraling cooling fluid line 120 a′ of the coolingplatform 102 a′ of FIG. 4E). That is, the cooling fluid line 120 acreates a series of progressively smaller diameter, circular coolingfluid line paths 132 a-f as the cooling fluid line 120 a winds from theinlet 128 to the outlet 130. Each cooling fluid line path 132 a-fprovides cooling to the cooling platform 102 a at an approximately equalradial distance along its path (unlike a cooling fluid line that spiralsinward). Cooling uniformity thereby may be increased.

To achieve the progressively smaller diameter, circular fluid line paths132 a-f, the cooling fluid line 120 a is provided with a series of bends134 a-e (FIG. 4C). In at least one embodiment of the invention, thebends 134 a-e are positioned proximate the outlet 130 (as shown in FIG.4C). Positioning the bends 134 a-e proximate the outlet 130 maycompensate for heating of cooling fluid as it travels from the inlet 128to the outlet 130 by providing more cooling fluid line surface areaproximate the outlet 130 (as described further below). The bends 134 a-emay be, for example, elliptical. The amount of bending may be controlledto increase or decrease flow resistance through the cooling fluid line120 a.

In at least one embodiment, the cooling fluid line 120 a is coupled tothe manifold 104 by brazing the inlet 128 and the outlet 130 of thecooling fluid line 120 a to an input line 132 and an outlet line 134 ofthe manifold 104, respectively (FIG. 4A). The cooling fluid lines 120b-c of the cooling platforms 102 b-c may be similarly configured. In oneembodiment, each cooling fluid line comprises ⅜ inch outer diameter and0.475 inch inner diameter tubing. Other tubing sizes may be employed(such as larger tubing sizes that allow for larger flows).

To cool the cooling platforms 102 a-c, water or some other cooling fluidis introduced under pressure to the input line 132 of the manifold 104.Exemplary input fluid pressures include 60-80 p.s.i., although otherpressures may be employed. Assuming the flow resistances of the coolingfluid line 120 a-c of each cooling platform 102 a-c are approximatelyequal, the cooling fluid supplied to the input line 132 of the manifold104 should flow approximately simultaneously to and approximately at thesame flow rate through each cooling platform 102 a-c. Each coolingplatform 102 a-c (and any semiconductor wafers placed thereon via thelift pins 114 a-c) thereby may be cooled.

With regard to the cooling fluid line 120 a (and the cooling fluid lines120 b-c of the cooling platforms 102 b-c), cooling fluid travels fromthe input line 132 of the manifold 104 to the inlet 128 of the coolingfluid line 120 a, through the cooling fluid line 120 a and out theoutlet 130 to the output line 134 of the manifold 104. In the embodimentof FIGS. 4B and 4C, the inlet 128 and the outlet 130 of the coolingfluid line 120 a are positioned close to one another. The lateraldimensions of the manifold 104 thereby may be reduced.

As shown in FIGS. 4A-C, each cooling platform 102 a-c is primarilycircular, so as to mimic the shape of a semiconductor substrate and toincrease cooling uniformity. A neck region 136 a-c of each coolingplatform 102 a-c may have the same width as the manifold 104 (as shownin FIG. 4A and FIG. 4C). Note that while a smaller neck region 136 a-cmay result in more uniform cooling, a smaller neck region 136 a-c alsomay make supporting each cooling platform 102 a-c more difficult. Othercooling platform shapes may be employed.

As shown in FIG. 4B, each cooling platform 102 a-c may be provided withholes (not shown) that receive rods 138 a-b for holding/positioning theplatform 102 a-c relative to the manifold 104. A screw, bolt or otherfastener (not shown) may be used to pull each cooling platform 102 a-cagainst the manifold 104 (e.g., so that the cooling platforms 102 a-cand the manifold 104 are perpendicular). Other fastening techniques maybe similarly employed.

The cooling platforms 102 a-c may be air cooled rather than liquidcooled. For example, the bottom portion 118 a-c of each cooling platform102 a-c may be vented to increase air flow (e.g., using a heatsinkpattern).

With reference to the exploded side elevational view of FIG. 5, aninventive valve assembly 213 may be employed within the processingsystem 11, or within any tool that benefits from a mechanism forselectively sealing an opening 214 of a chamber CH and deterringparticles and/or gas from traveling into and/or out of the chamber CHwhen the chamber opening 214 is not sealed.

The valve assembly 213 may comprise a housing 215 for coupling theassembly 213 adjacent the chamber opening 214 to be sealed. The housing215 includes at least a first opening 217 through which a substrate maybe transferred to the chamber opening 214, and a threshold portion 219positionable adjacent the chamber opening 214. A plurality of inlets 220may be formed in the threshold portion 219 and adapted to supply acurtain of gas across the chamber opening 214. The gas may be supplied,for example, from a gas source S (e.g., a source of an inert gas such asnitrogen, argon, or the like). For clarity, only one of the inlets 220is shown being coupled to the gas source S. The inlets 220 may bepositioned at other locations, such as along one or both sides of thehousing 215.

As shown in FIG. 5, a sealing surface 221 may be coupled to the housing215 and adapted to raise and lower with respect to the housing 215 so asto selectively (1) seal the chamber opening 214; and (2) retract fromthe chamber opening 214.

One or more openings 223 (which may be coupled to a vacuum pump P) arealso provided in the housing 215 so that the flow of gas from the gassupply inlets 220 may be exhausted therethrough. For clarity, only oneof the openings 223 is shown being coupled to the pump P. The openings223 may be positioned at other locations, such as along one or bothsides of the housing 215.

In one embodiment the gas supply S may be omitted and the interiorregion of the housing 215 may be vacuum pumped (e.g., via pump P) toensure that the interior region of the housing 215 is at a lowerpressure than the processing chamber CH before the processing chamber CHopens. Particles thereby may be prevented from flowing into the openprocessing chamber CH. Likewise, any gases which may remain in theprocessing chamber CH may be pumped out via the valve assembly's exhaustopenings 223. In another embodiment, the vacuum pump P may be omittedwhile only the gas source S is employed.

The sealing surface 221 of the valve assembly 213 may be coupled to aninflatable member 225 that can be selectively inflated and deflated soas to selectively press the sealing surface 221 against the chamberopening 214 and retract the sealing surface 221 from pressing againstthe chamber opening 214. In one embodiment a pair of sealing surfaces(e.g., a first and a second sealing plate 221 and 227) may be positionedon opposite sides of the inflatable member 225 such that inflation ofthe inflatable member 225 presses both the first sealing plate 221against the chamber opening 214, and the second sealing plate 227against the opening 217 in the housing 215. Exemplary sealing surfaces221, 227 and inflatable member 225 are described in U.S. Pat. No.6,347,918, issued Feb. 19, 2002 titled “Inflatable Slit/Gate Valve” andU.S. Provisional Patent Application Ser. No. 60/216,918 filed Jul. 8,2000, titled “Vacuum Assisted Door Assembly”, both of which describevalve assemblies which may be modified to include the threshold portion219 of the present invention, and both of which are incorporated hereinin their entirety by this reference.

In operation, whenever the sealing surface 221 is retracted from contactwith the chamber opening 214, inert gas (e.g., nitrogen from the gassource S) is supplied through the plurality of inlets 220 formed in thethreshold portion 219. The gas flow may be initiated, for example, justbefore the chamber opening 214 is unsealed. In one embodiment, acontroller 229, which may or may not be used to control processingwithin the chamber CH, is coupled to pressure detectors D (only one ofwhich is shown in FIG. 5) which receive pressure readings from theprocessing chamber CH and/or from the interior region of the valveassembly 213. The controller 229 also may be coupled to the pump P andthe gas source S for controlling pumping from and/or gas delivery to theinterior region of the valve assembly 213. The controller 229 may adjustthe pressure of the interior region of the valve assembly 213 (e.g., byvacuum pumping the region at a greater rate than the inert gas flowthereto (if any), so that contaminants will be deterred from enteringthe processing chamber CH, and/or so that potentially harmful chambergases will be removed as soon as they escape from the processing chamberCH).

The diameter and spacing between the inlets 220 is chosen together withthe flow rate of the gas so that a continuous laminar curtain of gasflows across the chamber opening 214. In this manner the gas flow fromthe inlets 220 may immediately carry any chemicals which may escape fromthe chamber opening 214 to the exhaust (e.g., via openings 223). Forexample, if the inventive valve assembly 213 is employed within theprocessing system 11 (FIG. 1), any harmful chemicals employed within theprocessing chambers 19 a-b may be prevented from entering the transferchamber 13. The inventive slit valve assembly 213 is particularlyadvantageous when employed to seal between a chamber that is maintainedat atmospheric pressure (and thus not pumped and purged like a vacuumchamber) and a processing chamber that employs toxic gases (e.g., achamber that performs a nitridization process that employs ammonium)whether or not the processing chamber operates at vacuum or atmosphericpressures. For example, the use of the valve assembly 213 may bedesirable when the processing chamber CH performs dry oxidationprocesses.

The number of inlets 220 and the number of outlets 223 need not be thesame, and the inlets and/or outlets may comprise any suitable shape(e.g., round, square, etc.). The controller 229 may include one or morecomputer program products for (1) detecting the pressure level withinthe interior region of the valve assembly 213 (e.g., via detectors D);(2) controlling/regulating flow of gas to the valve assembly 213 (e.g.,via a pressure regulator, flow controller, etc. (not shown) of the gassource S); and/or (3) controlling/regulating pumping of gas from thevalve assembly 213 (e.g., via a throttle valve (not shown) of the pumpP, by varying the speed of the pump P, etc.). Each computer programproduct described herein may be carried by a medium readable by acomputer (e.g., a carrier wave signal, a floppy disc, a compact disc, aDVD, a hard drive, a random access memory, etc.).

It will be understood that the housing 215 may include a back wallportion having an opening (both not shown) for positioning adjacent thechamber opening 214, or, as is shown in FIG. 5, the chamber wall may actas a back wall of the housing 215.

The foregoing description discloses only exemplary embodiments of theinvention; modifications of the above disclosed apparatus and methodwhich fall within the scope of the invention will be readily apparent tothose of ordinary skill in the art.

Accordingly, while the present invention has been disclosed inconnection with exemplary embodiments thereof, it should be understoodthat other embodiments may fall within the spirit and scope of theinvention, as defined by the following claims.

1 A substrate processing system comprising: a chamber having a pluralityof openings through which a substrate may be transported; a substratecarrier opener coupled to a first one of the plurality of openings; athermal processing chamber coupled to a second one of the plurality ofopenings; and a wafer handler contained within the chamber, having asubstrate clamping blade and a blade adapted to transport hightemperature substrates. 2 The system of claim 1 wherein the substrateclamping blade and the blade adapted to transport high temperaturesubstrates are vertically stacked. 3 The system of claim 2 wherein thewafer handler is adapted to elevate so as to position a desired one ofthe clamping blade and the blade adapted to transport high temperaturesubstrates at a desired elevation. 4 The system of claim 1 wherein theblade adapted to transport high temperature substrates comprises asensor for detecting the presence of a substrate properly positionedthereon. 5 The system of claim 1 wherein the substrate clamping bladecomprises a sensor for detecting the presence of a substrate properlypositioned thereon. 6 The system of claim 5 wherein the blade adapted totransport high temperature substrates comprises a sensor for detectingthe presence of a substrate properly positioned thereon. 7 The system ofclaim 1 further comprising a track contained within the chamber andhaving the wafer handler mounted thereon so as to travel therealong. 8The system of claim 1 further comprising a valve assembly forselectively sealing the second one of the plurality of openings, thevalve assembly comprising: a housing comprising a first opening on afirst side, and a threshold portion, the housing being adapted forcoupling to a chamber surface having an opening therein, such that asubstrate may be transferred through the first opening of the housingand the chamber opening and such that the threshold portion ispositioned between the first opening of the housing and the chamberopening; the threshold portion having one or more inlets adapted tosupply a curtain of gas across the chamber opening; and a sealingsurface positioned within the housing to selectively (1) seal thechamber opening, and (2) retract from the chamber opening so as not toobstruct substrate passage therethrough. 9 The system of claim 8 whereinthe blade adapted to transport high temperature substrates comprises asensor for detecting the presence of a substrate properly positionedthereon, and wherein the clamping blade comprises a sensor for detectingthe presence of a substrate properly positioned thereon. 10 The systemof claim 8 wherein the blade adapted to transport high temperaturesubstrates comprises a sensor for detecting the presence of a substrateproperly positioned thereon. 11 The system of claim 8 wherein theclamping blade comprises a detector for detecting the presence of asubstrate properly positioned thereon. 12 The system of claim 1 furthercomprising: a cooling station contained within the chamber. 13 Thesystem of claim 12 wherein the cooling station comprises a plurality ofcooling platforms. 14 The system of claim 13 wherein the plurality ofcooling platforms are vertically stacked. 15 The system of claim 13wherein the plurality of cooling platforms are cooled via a common fluidsupply that supplies pressurized fluid thereto. 16 The system of claim14 wherein the blade adapted to transport high temperature substratescomprises a sensor for detecting the presence of a substrate properlypositioned thereon, and wherein the clamping blade comprises a sensorfor detecting the presence of a substrate properly positioned thereon.17 The system of claim 14 wherein the blade adapted to transport hightemperature substrates comprises a sensor for detecting the presence ofa substrate properly positioned thereon. 18 The system of claim 14wherein the clamping blade comprises a detector for detecting thepresence of a substrate properly positioned thereon. 19 The system ofclaim 14 further comprising a valve assembly for selectively sealing thesecond one of the plurality of openings, the valve assembly comprising:a housing comprising: a first opening on a first side; and a thresholdportion, the housing being adapted for coupling to a chamber surfacehaving an opening therein, such that a substrate may be transferredthrough the first opening of the housing and the chamber opening andsuch that the threshold portion is positioned between the first openingof the housing and the chamber opening, the threshold portion having oneor more inlets adapted to supply a curtain of gas across the chamberopening; and a sealing surface positioned within the housing and adaptedto selectively (1) seal the chamber opening, and (2) retract from thechamber opening so as not to obstruct substrate passage therethrough. 20A substrate processing system comprising: a chamber having a pluralityof openings through which a substrate may be transported; and a waferhandler contained within the chamber having a substrate clamping bladeand a blade adapted to transport high temperature substrates. 21 Thesystem of claim 20 wherein the substrate clamping blade and the bladeadapted to transport high temperature substrates are vertically stacked.22 The system of claim 21 wherein the wafer handler is adapted toelevate so as to position a desired one of the clamping blade and theblade adapted to transport high temperature substrates at a desiredelevation. 23 The system of claim 20 wherein the blade adapted totransport high temperature substrates comprises a sensor for detectingthe presence of a substrate properly positioned thereon, and wherein theclamping blade comprises a sensor fox detecting the presence of asubstrate properly positioned thereon. 24 The system of claim 20 whereinthe blade adapted to transport high temperature substrates comprises asensor for detecting the presence of a substrate properly positionedthereon. 25 The system of claim 20 wherein the clamping blade comprisesa detector for detecting the presence of a substrate properly positionedthereon. 26 The system of claim 20 further comprising a track containedwithin the chamber and having the wafer handler mounted thereon so as totravel therealong. 27 The system of claim 20 further comprising: a valveassembly for sealing one of the plurality of openings in the chamber,comprising: a housing comprising: a first opening on a first side; and athreshold portion, the housing being adapted for coupling to a chambersurface having an opening therein, such that a substrate may betransferred through the first opening of the housing and the chamberopening and such that the threshold portion is positioned between thefirst opening of the housing and the chamber opening, the thresholdportion having one or more inlets adapted to supply a curtain of gasacross the chamber opening; and a sealing surface positioned within thehousing to selectively (1) seal the chamber opening, and (2) retractfrom the chamber opening so as not to obstruct substrate passagetherethrough. 28 The system of claim 27 wherein the blade adapted totransport high temperature substrates comprises a sensor for detectingthe presence of a substrate properly positioned thereon, and wherein theclamping blade comprises a sensor for detecting the presence of asubstrate properly positioned thereon. 29 The system of claim 27 whereinthe blade adapted to transport high temperature substrates comprises asensor for detecting the presence of a substrate properly positionedthereon.
 30. The system of claim 27 wherein the clamping blade comprisesa detector for detecting the presence of a substrate properly positionedthereon. 31 The system of claim 20 further comprising: a cooling stationcontained within the chamber. 32 The system of claim 31 wherein thecooling station comprises a plurality of cooling platforms. 33 Thesystem of claim 32 wherein the plurality of cooling platforms arevertically stacked. 34 The system of claim 32 wherein the plurality ofcooling platforms are cooled via a common fluid supply that suppliespressurized fluid thereto. 35 A substrate handler comprising: asubstrate clamping blade; and a blade adapted to transport hightemperature substrates. 36 The substrate handler of claim 35 wherein thesubstrate clamping blade and the blade adapted to transport hightemperature substrates are vertically stacked. 37 The substrate handlerof claim 36 wherein the wafer handler is adapted to elevate so as toposition a desired one of the clamping blade and the blade adapted totransport high temperature substrates at a desired elevation. 38 Thesubstrate handler of claim 35 wherein the blade adapted to transporthigh temperature substrates comprises a sensor for detecting thepresence of a substrate properly positioned thereon, and wherein theclamping blade comprises a sensor for detecting the presence of asubstrate properly positioned thereon. 39 The substrate handler of claim35 wherein the blade adapted to transport high temperature substratescomprises a sensor for detecting the presence of a substrate properlypositioned thereon. 40 The substrate handler of claim 35 wherein theclamping blade comprises a detector for detecting the presence of asubstrate properly positioned thereon. 41 The substrate handler of claim39 wherein the sensor comprises an emitter and a detector, and wherein anon-refractive material is positioned adjacent the emitter and thedetector so as to prevent an emitted signal from coupling through theblade to the detector. 42 A method of transporting a substrate,comprising: picking up a first substrate with a clamping blade of asubstrate handler; clamping the first substrate via the clamping blade;transporting the first substrate to a thermal processing chamber via theclamping blade; processing the first substrate within the thermalprocessing chamber to thereby heat the first substrate; extracting theheated first substrate from the thermal processing chamber via a bladeof the substrate handler that is adapted to transport a high temperaturesubstrate; and transporting the heated first substrate via the hightemperature blade. 43 The method of claim 42 wherein transporting thesubstrate to the thermal processing chamber via the clamping bladeoccurs at a higher speed than the speed at which the heated substrate istransported via the high temperature blade. 44 The method of claim 42further comprising placing a second substrate in the thermal processingchamber via the clamping blade after the heated first substrate isextracted from the thermal processing chamber, and while the heatedfirst substrate is held by the high temperature blade, such that thesubstrate exchange occurs without intermission. 45 The method of claim44 further comprising sensing, via a clamping blade sensor, whether theclamping blade has properly clamped a substrate prior to transportingthe substrate to another processing location. 46 The method of claim 44further comprising sensing, via a high temperature blade sensor, whethera substrate is properly positioned on the high temperature blade priorto transporting the substrate via the high temperature blade. 47 Themethod of claim 45 wherein the clamping blade comprises a detector fordetecting the presence of a substrate properly positioned thereon. 48The method of claim 45 further comprising signaling an error if properplacement of a substrate is not sensed on the clamping blade andpreventing transport of the improperly placed substrate. 49 The methodof claim 46 further comprising signaling an error if proper placement ofa substrate is not sensed on the high temperature blade and preventingtransport of the improperly placed substrate. 50 The method of claim 44further comprising transporting the first heated substrate to a coolingplatform. 51 A valve assembly adapted to seal an opening in a chamber,comprising: a housing comprising: a first opening on a first side; and athreshold portion, the housing being adapted for coupling to a chambersurface having an opening therein, such that a substrate may betransferred through the first opening and the chamber opening and suchthat the threshold portion is positioned between the first opening andthe chamber opening, the threshold portion having one or more inletsadapted to supply a curtain of gas across the chamber opening; and asealing surface positioned within the housing to selectively (1) sealthe chamber opening, and (2) retract from the chamber opening so as notto obstruct substrate passage therethrough. 52 The valve assembly ofclaim 51 wherein the housing includes one or more openings adapted toexhaust gas from an interior region of the housing. 53 A systemcomprising: a chamber having an opening in a chamber surface; a valveassembly adapted to seal the opening in the chamber surface, comprising:a housing comprising: a first opening on a first side; and a thresholdportion, the housing being adapted for coupling to the chamber surfacehaving the opening therein, such that a substrate may be transferredthrough the first opening and the chamber opening and such that thethreshold portion is positioned between the first opening and thechamber opening, the threshold portion having one or more inlets adaptedto supply a curtain of gas across the chamber opening; and one or moreopenings adapted to exhaust gas from an interior region of the housing;a sealing surface positioned within the housing to selectively (1) sealthe chamber opening, and (2) retract from the chamber opening so as notto obstruct substrate passage therethrough; and a controller programmedto: control a flow of gas through the one or more inlets into theinterior region of the housing; and control a flow of gas through theone or more openings out of the interior region of the housing. 54 Amethod comprising: providing a processing system having: a transferchamber; a processing chamber coupled to the transfer chamber, theprocessing chamber having an opening that allows a substrate to betransferred between the transfer chamber and the processing chamber; anda valve assembly coupled to the processing chamber and adapted toselectively seal the opening of the processing chamber, the valveassembly having an interior region adjacent the opening of theprocessing chamber; vacuum pumping the interior region of the valveassembly; and exhausting any gas removed from the interior region of thevalve assembly by the vacuum pumping. 55 The method of claim 54 whereinvacuum pumping the interior region of the valve assembly comprisesvacuum pumping the interior region of the valve assembly to a vacuumlevel below that of the processing chamber and the transfer chamber. 56The method of claim 55 wherein exhausting any gas removed from theinterior region of the valve assembly by the vacuum pumping comprisesremoving gas emitted through the opening of the processing chamberbefore the gas enters the transfer chamber, 57 The method of claim 55wherein vacuum pumping the interior region of the valve assembly to avacuum level below that of the processing chamber and the transferchamber comprises; flowing an inert gas into the interior region of thevalve assembly at a first rate; and removing the inert gas from theinterior region of the valve assembly at a second rate that is greaterthan the first rate. 58 The method of claim 55 wherein vacuum pumpingthe interior region of the valve assembly to a vacuum level below thatof the processing chamber and the transfer chamber comprises: detectinga pressure level within the interior region of the valve assembly; andadjusting at least one of a flow rate of gas into the valve assembly anda flow rate of gas out of the valve assembly so that the vacuum level ofthe interior region of the valve assembly is below that of theprocessing chamber and the transfer chamber. 59 A method comprising:providing a processing system having: a processing chamber having anopening that allows a substrate to be loaded into the processingchamber; and a valve assembly coupled to the processing chamber andadapted to selectively seal the opening of the processing chamber, thevalve assembly having an interior region adjacent the opening of theprocessing chamber; and flowing a gas through the interior region of thevalve assembly so as to generate a curtain of gas across the opening ofthe processing chamber. 60 The method of claim 59 further comprising:vacuum pumping the interior region of the valve assembly; and exhaustingany gas removed from the interior region of the valve assembly by thevacuum pumping. 61 The method of claim 59 wherein vacuum pumping theinterior region of the valve assembly comprises vacuum pumping theinterior region of the valve assembly to a vacuum level below that ofthe processing chamber. 62 A method comprising: providing a processingsystem having: a processing chamber having an opening that allows asubstrate to be loaded into the processing chamber; and a valve assemblycoupled to the processing chamber and adapted to selectively seal theopening of the processing chamber, the valve assembly having an interiorregion adjacent the opening of the processing chamber; and vacuumpumping the interior region of the valve assembly so as to remove gasemitted from the opening of the processing chamber. 63 An end effectorfor transporting a substrate, comprising: a blade adapted to support asubstrate within a first plane defined by the blade; and a sensor fordetecting the presence of a substrate on the blade, the sensorcomprising an emitter adapted to emit a beam such that the beam iswithin the first plane and a detector adapted to receive and detect thebeam, the emitter and detector being coupled to the blade such that asubstrate supported by the blade within the first plane interrupts thebeam. 64 The end effector of claim 63, wherein the beam is a light beam.65 The end effector of claim 63, wherein the beam is a light beam, andwherein the blade comprises a refractive material that will allow lightto couple therethrough. 66 The end effector of claim 65 wherein therefractive material is adapted to withstand a temperature greater than70° C. 67 The end effector of claim 65 wherein the refractive materialis adapted to withstand a temperature of 600° C. 68 The end effector ofclaim 65, wherein the refractive material of the blade comprises quartz.69 The end effector of claim 65, further comprising a non-refractivematerial adjacent the sensor so as to prevent light from coupling withthe refractive material of the blade. 70 The end effector of claim 69,wherein the non-refractive material comprises a coating. 71 The endeffector of claim 69, wherein the non-refractive material comprisessilicon carbide. 72 The end effector of claim 69, wherein the detectoris at least partially surrounded by the non-refractive material so as todeter erroneous detection of reflected or refracted light from the lightbeam. 73 The end effector of claim 72, wherein the non-refractivematerial comprises metal. 74 The end effector of claim 64, wherein abeam gain threshold of the sensor is adjustable so as to allowcompensation for reflection and refraction of the light beam. 75 The endeffector of claim 74, wherein the blade comprises a refractive materialthat will allow light to couple therethrough. 76 The end effector ofclaim 69, wherein the emitter is at least partially surrounded by thenon-refractive material so as to deter reflection or refraction of thelight beam. 77 A method of positioning a substrate on a blade anddetermining whether the substrate is properly positioned thereupon,comprising: providing an end effector comprising: a blade comprising arefractive material, the blade being adapted to support a substratewithin a first plane; and a sensor coupled to the blade for detectingthe presence of a substrate on the blade, the sensor being adapted toemit a beam such that the beam is within the first plane and to receiveand detect the emitted beam; positioning a substrate on the blade; anddetermining whether the substrate is properly positioned on the bladebased on whether the sensor detects or fails to detect the beam. 78 Themethod of claim 77, further comprising preventing movement of the endeffector if the sensor detects the beam. 79 The method of claim 77,further comprising providing a controller in communication with thesensor, adapted to prevent movement of the end effector if the sensordetects the beam.